166 PKESSURE UPON THE BASE OF VESSELS. 



In a vessel which is wider at the top than at the 

 bottom, fig. 115, the lateral pressure acting perpen- 

 dicularly to the sides, as indicated by the arrows, 

 is not horizontal, and the pressure at two opposite 

 points in the same horizontal layer is therefore not 

 exactly opposite, but at both sides it is directed down 

 wards, tending to press the sides down, not directl) 

 asunder ; consequently, both sides and base have to beai 

 a downward pressure. The total downward pressure 

 must obviously in this case also be equal to the weight 

 of the liquid, but part of it is borne by the sides, and it 

 follows that, in a vessel which becomes gradually nar- 

 rower towards the base, the pressure upon the bottom it 

 less than the weight of the contained liquid. The pressure 

 upon the bottom of the vessel represented in fig. 1L F 

 is equal to the weight of the liquid column a b d c, thai 

 is, it is the same as that upon the bottom of the vesse 

 in fig. 114, if the area of the base and the depth o 

 liquid are the same in both vessels, and the liquids ar< 

 also the same. 



If the sides of a vessel be inclined inwards, as ii 

 fig. 116, the lateral pressure is directe< 

 outwards and upwards : the sides ar< 

 pressed away from each other, but a 

 the same time in a manner which wouL 

 separate them from the base, in ai 

 upward direction, if they could mov 

 freely. Whatever the weight of th 

 FIG. 116 ($ real size}, liquid in the vessel, that will als 

 be the force with which the bottom presses against t\\ 

 scale-pan. But this cannot be the whole pressure upo 

 the base, for the pressure transmitted to the scale-pa 



